Influence of Machine-Side Converter Diode Selection on the Lifetime of Type-4 Wind Turbine Power Converters

Inhalt:
Type-4 wind turbine power converters provide better grid compliance performance that is essential for effectively integrating more renewable energy sources into the electrical network. The lifetime of the converters should be concerned during the design and operation phases as well as efficiency of the system. In this study, a lifetime enhancement method is proposed for back-to-back connected power converters of Type-4 wind turbines. The technique is to place Si or SiC diodes with partial current ratings in parallel to existing Si diodes of IGBT modules within MSCs (machine side converters). The lifetime of back-to-back connected power converters is mostly determined by the MSC, and especially by the diodes. Therefore, any precaution which limits or decreases the diode junction temperatures will contribute to improve the lifetime of the converter system. In the study, Si and SiC devices have been evaluated and the results are benchmarked with the case having only existing Si diode of IGBT modules. The proposed method is developed and tested in PSCAD (wind turbine and converter model development) and MATLAB (thermal model development and lifetime calculations) tools. The results reveal the effectiveness of the proposed method.